This invention relates to brake release mechanisms for railroad cars and more specifically to a mechanism for automatically releasing a railroad car hand brake upon movement of the car.
Movement of a rail car with hand brake applied can result in putting flat spots on the wheels of the car, possible derailment of the car or damage to trucks and brakes of the car. Prior attempts have been made to address this problem. U.S. Pat. No. 591,666, issued Oct. 12, 1897, discloses a lever connected to a piston movable by a brake cylinder to which air is supplied. Movement of this lever produces movement of a brake rod which, in turn, moves a second lever to disconnect a pawl from a ratchet wheel. Such an arrangement might be utilized with a rail car hand brake. U.S. Pat. No. 591,667, issued on the same date, discloses an angle cock which is opened to connect a train line to a railroad car. The cock has a handle which, when turned to open the cock, causes movement of a linkage which disconnects a pawl from a handbrake ratchet thus releasing the brake. U.S. Pat. No. 3,891,277, issued June 24, 1975, discloses an actuating valve to which air is directed. The valve has a piston movable by air pressure to open an outlet through which air is directed to a handbrake release cylinder.
The mechanisms described in these patents do produce release of a railroad car handbrake when the car's air brakes are released by trainline pressure or it is sensed that the trainline is connected. There are, however, situations where the trainline is connected and the airbrakes are released, but it is still necessary to keep the hand brake applied. Such a situation occurs, for example, where a train is assembled and the air brakes tested before the locomotive is connected.